Implement shapecheck for more primitives (#1990)
* shapecheck of jit, device_put, broadcast_in_dim, better error for unsupported ops, parse multi-digit integer literals
* WIP shapecheck np.pad
* Implement shapecheck of gather, pad
* Fix shapecheck of pad
* Implement polymorphic shape rule for (strided/dilated) convolution, refactor
* Cleanup
* Fix
* Remove all polymorphic shape rules, reuse shape rules instead.
* Register shape_rule for all standard_primitives
* Remove ShapeExpr, canonicalize_poly, renames
* Complete shapecheck(binop) implementation, remove special cases for polymorphic shapes
* Allow Poly of form d*poly + k to be divided by d
* Fix bug, inline poly_without_zeros.
